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--- a/src/internfile/mh_mbox.cpp
+++ b/src/internfile/mh_mbox.cpp
@@ -18,6 +18,8 @@
  *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  */
 #ifndef TEST_MH_MBOX
+#include "autoconfig.h"
+
 #include <stdio.h>
 #include <fcntl.h>
 #include <errno.h>